1. Field
The present application pertains to the field of aeronautics, and in particular nacelles for aircraft. More precisely, the present application relates to an aircraft nacelle for a double-flow engine equipped with at least one thrust reverser.
2. Brief Description of Related Developments
It is known how to equip an aircraft with nacelles, each of which holds a direct-reaction engine, to assure its motions on land and in the air. Each nacelle is mounted on the lower surface of the wings. Air is drawn into the nacelle at the position of a front extremity of this nacelle, located at the front side of the aircraft. The nacelle ejects the absorbed air at high velocity toward the rear of the aircraft.
To provide for forward motion of the aircraft, it is necessary for an air mass passing through the nacelle to have a discharge velocity greater than the its intake velocity. The discharge velocity of the air mass is increased by a known method inside the nacelle.
The air passing through the nacelle is composed of two different flows. A first flow, called the primary flow, passes through the engine. The primary flow is ejected directly out of the nacelle from the rear of the engine. A second flow, called the secondary flow, passes through an air passage channel before being ejected outside of the nacelle. The air passage channel is arranged between an internal wall of a cowling of the nacelle and an external wall of the engine, and extends along the turbojet engine.
It is then known how to mount these thrust reverser nacelles to reduce the landing distance of the aircraft. Landing distance of the aircraft means the distance traveled by the aircraft between the moment when the landing gear of the aircraft touches the runway and the moment when the aircraft comes to a complete stop on the runway. These thrust reversers deflect part or all of the air flows departing at the rear of the nacelle, to eject them toward the front of the aircraft. These thrust reversers thus create an aerodynamic drag and accordingly a braking force called a “counterthrust,” which contributes to the slowing of the aircraft.
Various thrust reversers are known from the prior art, such as thrust reversers with pivoting doors, or thrust reversers with grilles.
The document U.S. Pat. No. 3,829,020 discloses thrust reversers with a cowling that is movable in translation, which releases a door to rotate, and thus to block the flow of cold air and to modify its trajectory by expelling it to the side.
A nacelle equipped with thrust reversers with pivoting doors is also known, which has doors arranged within the thickness of the nacelle cowling. These doors are distributed around a circumference of the nacelle. In the inactive position, the doors are closed, in other words they extend in an extension of the cowling. In the active position, the doors are open. The displacement of the doors is such that a portion of the doors then extends toward the outside of the nacelle. A pivot axis of the doors is at a distance from a pivoting extremity of these doors. By pivoting extremity is meant the extremity of the doors on which the pivot axis is arranged. Thus, when the doors are open the pivoting extremity of the doors is located inside the nacelle, and at least partially obstructs the air passage channel. The flow of air is then blocked, and is evacuated outside of the nacelle through an orifice opened up by the opening of the doors. The portion of the doors that extends out of the nacelle provides for directing the flow toward the front of the nacelle.
Depending on the position of the doors on the cowling, the thrust reversers provide for a reversal of the thrust derived solely from the secondary flow, or the thrust derived from the primary air flow and from the secondary air flow. Actually, if the openings obstructed by the doors of the thrust reversers are arranged at a rear extremity of the cowling, the primary flow is evacuated through these openings, at the same time as the secondary flow. On the other hand, if the openings are arranged upstream from the primary flow, only the secondary flow is evacuated through the openings on the cowling.
The document FR 2 887 225 discloses a nacelle equipped with thrust reversers. Each thrust reverser is equipped with an internal door and an external door, with each of these doors having a unique direction of displacement. These two directions of displacement are opposite one another, so that when the thrust reverser is in the active position the external door sends the flow of air blocked by the internal door in the interior of the nacelle, toward the front of the nacelle. Locking means are provided to guarantee that no untimely opening of the doors can be produced when the aircraft is in flight.
But these thrust reversers with pivoting doors are currently associated with burdensome constraints of maintenance and design linked to the risk of untimely opening in flight, which can cause the loss of the airplane.
Accordingly, there is a pressing need for a nacelle equipped with thrust reversers that stay closed or that close in case of a failure, for example of the control device that provides for the sifting of these doors between the active and inactive positions.